It is known that a diaryl carbonate can be prepared from a diaryl oxalate by decarbonylation. The known process, however, is not favorably employable in industry because the reaction rate is very slow and the yield and selectivity are low.
Yuki Gosei Kagaku Kyokaishi (Journal of Synthetic Organic Chemistry, Japan), Vol.5, No.4-9, Report 47, pp. 70-71(1948) teaches a reaction in which diphenyl oxalate is heated to release carbon monoxide to give diphenyl carbonate. This report describes neither yield nor selectivity. According to a trace experiment of the experiment of this report, only a small amount of diphenyl carbonate is produced.
U.S. Pat. No. 4,544,507 describes that the carbonic acid dialkyl ester, i.e., dialkyl carbonate, can be prepared by heating a dialkyl oxalate in a liquid phase at 50.degree.-150.degree. C. in the presence of an alcolate catalyst. In the working example of the Patent publication, the diphenyl oxalate is heated in the presence of a potassium phenoxide catalyst only to give mainly the diphenyl oxalate, namely, the starting compound.